The present invention relates to a semiconductor laser.
In semiconductor lasers, conventionally, it is known that increases in optical outputs can cause deterioration of cavity end faces, i.e., COD (Catastrophic Optical Damage). The COD is due to increases in temperature of the cavity end faces involved in high-power operations of semiconductor laser devices. In particular, a high-power semiconductor laser having a reduced reflectivity of a light-emitting end face, which is one of cavity end faces, the temperature increase of the light-emitting end face would be large, causing COD to occur at the light-emitting end face. Thus, it is necessary to improve heat radiation in vicinities of the light-emitting end face.
FIG. 5 shows a schematic perspective view of main part of a conventional semiconductor laser described in JP 2003-31901 A. In FIG. 5, part of the conventional semiconductor laser is removed so that the multilayered structure of the conventional semiconductor laser becomes easier to understand.
The semiconductor laser, as shown in FIG. 5, has an n-type GaAs substrate 512, a main body 550 formed on the n-type GaAs substrate 512, and a p-side plated electrode 530 formed as a so-called overcoat electrode to the main body 550.
The main body 550 includes an n-type buffer layer 514, an n-type AlGaInP clad layer 516, a multiquantum well active layer 518, a p-type AlGaInP clad layer 520, a p-type GaAs contact layer 522 and a SiO2 film 528, as these are formed on the n-type GaAs substrate 512.
In the p-type AlGaInP clad layer 520, a ridge stripe portion 540 extending along a longitudinal direction of the cavity is formed. The upper surface of the ridge stripe portion 540 is covered with the p-type GaAs contact layer 522, and both side faces of the ridge stripe portion 540 are covered with the SiO2 film 528.
Also, a portion in the vicinity of a light-emitting end face 550a of the main body 550 is a window region 532 formed by introduction of zinc. On the window region 532, the p-side plated electrode 530 is not formed. That is, the p-side plated electrode 530 is formed except for portions in the vicinity of the light-emitting end face 550a of the main body 550.
It is noted that reference numeral 534 in FIG. 5 denotes an n-side electrode.
A method for mounting the above-described conventional semiconductor laser onto a stem is described in JP 2004-214441 A.
According to this mounting method, the main body 550, as shown in FIG. 6, is joined by a low-melting-point solder material 602 to a submount 601 that functions as a heat sink. The submount 601 is joined to a high-thermal conductivity stem 603 by bonding resin 604. Such a state is called “junction down” since a pn junction is positioned on the heat sink side, i.e., on the submount 601 side.
Also, the junction between the main body 550 and the submount 601 is done in such a manner that the light-emitting end face 550a of the main body 550 projects from the end face of the submount 601. By doing so, laser light emitted from the light-emitting end face 550a can be prevented from being interrupted by the submount 601, and moreover the laser light can be prevented from being interrupted by sticking of the low-melting-point solder material 602 to the light-emitting end face 550a. 
However, since the junction of the main body 550 to the submount 601 causes the light-emitting end face 550a to project from the end face of the submount 601, heat generated in vicinities of the light-emitting end face 550a of the main body 550 cannot efficiently be transferred to the submount 601. This poses a problem of poor heat sinkability at portions in vicinities of the light-emitting end face 550a of the main body 550.